Analytic studies to determine risk factors for Alzheimer's disease (AD) are planned or being conducted. A large case-control study of head trauma with loss of consciousness as a risk factor for AD has been completed in Rochester, MN. There was no detected increase in risk of AD following head trauma. A case-control study of Alzheimer's disease is in progress in White Plains, New York. An attempt has been made to evaluate and improve instruments used in case-control studies of dementia.